Sure, hit it with cloth and then measure it again. If it's off a little bit have a machine shop circle it and use a different bearing. These older motors are so over engineered that they can get away with some weird shit, but keeping things round helps a lot and it's worth it now as prices keep going up.

 

It's not a valve lap thing where it's crazy pressure. You could get away with a thicker oil as is if you can't even feel the galling. I wouldn't, but many would. Cheaper in the long term to just smooth out the whole thing and have it balanced if needed, and then have someone clearance it for the temps and weights you're going to be using it in so you don't have to worry about rebuilding it again and searching for shit in five years.

 

I'm tempted to just have a shop resize it for me, considering the main and rod journals are right at or 0.0001" below the specified tolerance. Honestly I don't mind the extra cost too much, but the big problem is all the good shops are booked up for months. I REALLY want to drive my car this summer

 

Up to you man. Smooth it out a bit, measure it, see how out of round it is. Run a little heavy if it's just for a few miles and then wait for things at the shop to cool down. Up to you and what you want to do and what you think the engine can take now and what kind of work you want done.
I've beat the fuck out of my 90 Honda Beat becuase the stand-alone is done and tuned, and it's being used as a prototype for a turbo kit prior to being a dedicated dirt rallycross car. Every car has its purpose, think about what it would cost to do what you want, and how expensive it would be to do it tomorrow VS later when you plan on doing stuff and buying parts.

 

I'll say, my shop is my brother, and he's delayed a lot of stuff for me. People are paying top dollar for stuff now. If someone gave you a 'shop discount' or something, I'd pass. Now is not the time to rush anything. I have shit on hold and don't even care about paying for storage because I want it done right.

 

That can easily be polished right out by you, a shoelace and some fine sandpaper. Google it. Piece of cake. I polished my 7M crank this way and it's smooth as glass. People above suddenly started saying its not round though? Was that .0001 measurement a roundness spec or a total diameter spec? Either way, I agree this is not rocket science to polish off. You could even use a piece of curved plastic (section of PVC pipe, etc) with the paper on the inside to initially knock the high spots off your scratches, then proceed to polish. Don't get too hung up on this - you can easily manage what are very minor scratches.

Know this, too. Don't try to eliminate the scratch. Under a microscope there is a scratch INTO the metal and two ridges on each side of it that are proud of the surface. The ridges are all you want to get rid of as they'll intrude into your oil film toward the bearing. They will come off very fast and easily, but don't try to keep polishing until the mark INTO the metal is gone. That's pointless, taking off metal then, and opening oil clearance.

 

It's the cat chasing the tail bit with the roundness and smoothing out a groove. You can't tell either by a picture. If it's a smaller thing, fuck it, run it for a while. It's cheaper now to do that for a while and tear it down instead of building new when it comes down to people with situations like this that want to run on a budget. You're going to get paid either way, and the customer might luck out in this case. The other option is lose lose for them, rebuilding everything and all the labor involved.
I'm all for grinding all metal away. I hate weight. I have a couple of shit hondas with Ti rods in them just to keep the weight down so they spin a little higher. (had, blew one up)

 

Picked up some 3M 1200 wetordry and blue magic metal polish on amazon. Thanks for the tips lads. I'll have the crank sorted out by this weekend. BTW, my micrometer was reading .0004" under which I actually forgot to account for 🥴 so I'm well within spec on everything. As for the roundness, I measured each journal on 2 perpendicular axis. The measurements were all within .0001" of each other.

 

Good call. You'll get done, see the shiny finish you've created, and laugh at how simple that was. Wider shoelaces are better simply because they spread the pressure a bit. In my anal-ness, I counted the back and forth moves until I could tell I was making a difference, and I wetted 1000 grit with WD40 which is actually more of a cleaner and recommended. Once I got to the number that made a difference on one journal, I just wildly did the same count on each successive journal. I think it was like 120 moves - each direction was a move and I kinda rolled the crank around a bit to spread whatever pressure, and also pulled as much from opposite sides (vs sawing them right next to each other straight up and down) also with an eye toward spreading the load/sanding pressure. That made it perfectly smooth and a low gloss, and it worked out extremely well. You'll need less of everything - just knock the ridge off each side of the scratch, polish a bit and you're done. I say that because your journals look fine except the marks you made, whereas mine had sat 19 years and had mineral deposits and water stains. I do suggest a piece of curved plastic to quickly knock down the ridges you created along the scratches, then go with the shoelace full polish and then your metal polish for the win! Otherwise, I think the shoelaces will glide over the ridges many cycles as they're flexy, where the curved plastic will hit only the high ridges you made and knock them down fast so you can move to polishing.

 

@IdahoDoug, you're a bad ass. Been meaning to tell you that for a while... You too @signalpuke.


Ken.

 

Gents, standard main bearings are out of stock EVERYWHERE. All I can find in-stock is ACL's HX series with an extra .0001" of oil clearance. How bad is that to run on a street motor? I guess it depends on my current oil clearance... I'll get the plastigauge and see where it's at with my current bearings.

 

Just checked their catalogue because that didn't sound right. They're an extra .001", not a tenth. I wouldn't buy anything until you measure and see if you can run the looser set across the board.

 

Ken,
Wow, that's center of mass to my value system to hear that from you. Thanks.
PS - hope some of that is based on my Gen III "Father/Son project" thread, because I need some harassment to get back up to speed on the project!! Heh...

 

Idaho,

Definitely related to the "Father/Son Project". You've dispensed some serious knowledge in that thread, and I'm not ashamed to admit that some of it is over my head. That said, your posts and threads are great resources for the MKIII community in particular.


Ken.

 

Get back up to speed boomer

 

Cleared out the stall, put the tire back on, got it off jackstands out back where I'd been fixing the battery tray, and ready to stuff it back into the garage. May need an igniter argh. Nonturbo.

 

Ah, very cool. So there's something interesting about getting older it turns out you only fully understand when you are experiencing it. Once you've accomplished enough in life to do what you were meant for, you realize the currency of older people is respect, and a particularly important branch of that tree of respect it is the ability to dispense wisdom. I'm on the cusp of being "old" at 60 and am getting whiffs of that in the wind for myself. So it is with exceeding welcome that your words fall on me in that vein. Social trends make older people increasingly irrelevant, but the antidote to that are forums that become an excellent way for that transfer of knowledge to happen very effectively.

My Dad is an excellent teacher of all things, and he was a successful Engineer, fighter pilot and international airline captain. I still call him for questions, and in fact I called before I lapped the valves on my "Father/Son" Gen III project. From 70 years ago, he remembered and described to me the "tone change" you'll hear when the valves are properly seated.

I am honored by your kind words, and hope I can continue to share what others before me taught, because wrenching on your own car is a pastime that goes back 100 years now. In its day it was the #1 bonding activity between fathers and sons (and daughters) as little boys were inexorably drawn to the garage to see what makes those fascinating cars tick. That led to a cool career for me as a product developer for GM and Lexus and perhaps out there now is someone who dreams of one day being on a development team in the auto industry.

Anyhow, enough philosophizing. This thread got me re-focused on the Supra and I just walked in from pulling it into the garage with my son. It's clean, the mostly done engine is next to it and I'm officially on the job again. My brother in law from California will be here Sunday for a week, and he's a former Ford suspension engineer and fellow car buff so this is perfect timing. I have no doubt we'll spend some time yakking out in the garage. Regards, Doug.

 

sorry to dig up an old thread.. interested to know what action was taken with the crank journal scratches and outcome any issues?

 

Yeah it worked out just fine. I used 3m 1200 grit wet or dry, and I believe WD-40 as a lubricant.
Then I used blue magic metal polish. I cut a microfiber cloth into strips the width of the crank journal and polished it like a bowling ball.